Solid particles entrained in the flue gas of a circulating fluidized bed (CFB) boiler can be removed in a variety of ways. One method is to utilize an impingement-type collector that is positioned directly in the flow path of the flue gas. The theory being that as the solid particles strike the surface of the impingement members in the in-line collector, they will collect and fall into a hopper underneath the collector. A typical impingement-type collector utilizes an array of vertically suspended U-shaped members.
Because such in-line collectors increase flow resistance, care must be taken to prevent the flue gas from bypassing all or portions of the collector such as by flowing underneath it through the hopper. To prevent this, a bottom plate or pan is installed across the collector to channel the flue gas through it. This pan separates the collector from the hopper and prevents the flue gas from flowing into the hopper and across the top of the stored particles. If such flow or bypassing were permitted, some of the particles stored in this hopper would `spill over` or again become undesirably entrained in the flue gas.
For solid particles to collect in the hopper from the collector, however, there must be openings in this pan for these particles to pass through. Without such openings, the collected solids would plug the flue gas path by accumulating and sintering on the tightly packed impingement members of the collector. With such openings, however, an undesirable avenue for the passage of the flue gas into the hopper is created.
In an effort to control this situation in such collectors, the openings in the pan are restricted in size to fit entirely within the enclosed area of the vertically suspended members. Unfortunately, because of the large number of suspended members in impingement type collectors, these numerous openings reduce the pan's ability to prevent the flue gas from bypassing underneath the collector.
To prevent such by-passing, a box or cone with a smaller opening for discharge into the hopper was secured around and underneath each opening in the pan. Although this appeared to be a satisfactory solution, after some period of operation these boxes or cones were found to be plugged or nearly plugged as a result of the sintering of the collected particles.
Consequently, it is an object of this invention to devise a system whereby solid particles collected in an impingement-type collector are transferred to a storage hopper. Another object of this invention is a system that prevents the flue gas flowing through an impingement-type collector from bypassing this collector. A further object is a system that inhibits flue gas from flowing, in either direction, through the openings required for proper solids transport. These and other features of this invention will become obvious upon further investigation.